Prior art methods of providing temperature compensation of transistor circuits are numerous and include the use of large-valued swamping resistors placed in the emitter circuit to overcome the small value of the emitter-base junction resistance. Another method is to reduce the emitter-base forward bias as temperature increases. Both these methods have the disadvantage of seriously reducing gain often requiring an extra stage of amplification which only compounds the compensation problem.
It has also been proposed to use thermistors or temperature-sensitive resistors. However, since state-of-the-art transistors have a negative temperature coefficient at the base-emitter junction, the use of a thermistor, which also has a negative temperature coefficient, requires careful circuit design efforts to cause the thermistor to have the desired effect for compensating the base-emitter characteristic without degrading circuit performance. A similar problem involves the use of diodes since they also exhibit a negative temperature coefficient.